Field of the Invention
Embodiments of the present invention relate, in general, to a manual mechanism to fold a wing on an aircraft and more particularly to a manual wing-fold mechanism having independent load paths for flight loads and loads supporting the wing during the folding operation.
Relevant Background
Despite the technological advances in aviation, one only has to spend some time observing nature to recognize that many challenges with respect to aviation still lie before us. It has long been recognized that aircraft are difficult to house on the ground. They are by their very nature, awkward large crafts. The gangly wings and fuselage require a large space by which to cover and protect the craft from the elements. And as agile as an aircraft may be once airborne, its movement on the ground is one of lumbering cautiousness.
Yet a bird, as it smoothly transitions from flight to rest on a dowel, can quickly and efficiently fold its wings and squeeze through a hole not much larger than the size of its head. So it is not surprising that an efficient and timely means for stowing an aircraft's wings to aid in transportation and storage is a long felt need.
Several approaches for folding the wings of an aircraft to reduce its overall size have been developed. Many modern-day aircraft, especially military aircraft, are equipped with wing sections that can be folded or placed into a position that when not deployed for flight operations offers the ability for the aircraft to be stored and transported in a much more efficient manner. Examples of such aircraft include carrier-based aircraft in which the wings fold for compact storage and maintenance below deck. Other examples include sailplanes, which upon landing in locations away for their normal base of operations possess the ability to remove the wings so that the aircraft can be quickly loaded on a trailer for transportation.
In aircraft in which the wings fold but remain attached to the fuselage, the mechanisms must securely lock the wings in the deployed position for flying and also secure the wings in their folded position so that they are not inadvertently damaged from wind gusts or the like. As the wings are substantial components of the aircraft, they represent a significant amount of mass and are designed to translate aerodynamic loads from the wingtip to the wing root. These loads are conveyed via one or more spars that run along the length of the wing parallel to the lateral or pitch axis of the aircraft.
Typically, a folding mechanism utilizes these same large structural components, spars, to support the folding and/or rotation of the wing. While seemingly an efficient use of the wing's inherent structure, the complexity and necessary robustness of such a mechanism comes at the cost of weight. In large military aircraft this additional complexity and added weight is minimal in comparison to other design criteria, such as the structural requirements for landing on a carrier or for carrying external ordinance. However, in light recreational or utility aircraft, the weight and complexity of such a folding mechanism is unacceptable.
The most efficient use of space in which to store the wings is to align the wings in some manner with the fuselage. Generally such a mechanism uses a single motion to pivot the wings through an axis oblique to the fuselage. The Grumman Corporation carrier based aircraft use this type of wing-fold. A single motion fold, however, possesses some undesirable characteristics. For example, such a fold mechanism requires a section of the upper and lower wing surface to be removed or repositioned so that the folding portion does not intersect with the stationary portion. Single motion folds also create center of gravity concerns making the aircraft unstable during ground operations.
Therefore, what is needed is a wing-fold mechanism that is simple, robust and lightweight. Moreover, it is desirable that the folding mechanism be separate from the inherent structure of the wing that transfers aerodynamic loads from the wingtip to the wing root and that it be a manual process operable by a single individual. These and other challenges of the prior art are addressed by one or more embodiment of the present invention.
Additional advantages and novel features of this invention shall be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following specification or may be learned by the practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities, combinations, compositions, and methods particularly pointed out in the appended claims.